Try to find or estimate the density. Decide on the specific application you want and build an enclosure for it. If it is ~40 density, you should be able to make it into a decent portable bass trap. If it is rolled up tight, you will need to let it expand to get to the specified density.

If the density is too high, you will get excess reflection. For bass traps, lower density, such as that of fiberglass attic insulation or lower rockwool density is best if you are going beyond 5 or 6" thick.